Recreational
anglers are increasingly releasing part or all of their catch.
As more fish species are managed by minimum and even maximum
size limits, regulatory releases are more common. Growing
numbers of anglers are also voluntarily releasing some of
their catch that may have been legally kept. Some voluntary
releases are made to prolong a fishing trip. Other anglers
keep only "trophy" fish or enough fish for one meal.
Their intention is to leave more fish in the water to grow
to larger, more desirable sizes.

Neither
regulatory nor voluntary releases work if the fish released
die. At worst, release mortalities can result in overharvest,
even though the fish aren't kept. At best, the result is waste
of a valuable resource. Released fish may not die until days
after their release. Fish that are captured and released may
die for three reasons: angling stress, wounding or handling.

Angling
stress occurs during the fish's fight after hooking. The vigorous
physical exertion causes lactic acid wastes to build up in
the fish's muscles. This in turn leads to blood acidification
which can disrupt the metabolism of the fish. If a fish isn't
able to get its blood chemistry balanced back to prestress
levels, it may die, perhaps as long as 72 hours after the
catch.

The longer
a fish is played, the more lactic acid is built up in the
fish. Many fishermen like to use a light tackle to "give
the fish a fighting chance." This doesn't fit together
with catch and release fishing. If the catch is expected
to be released, anglers should use heavy enough tackle to
bring the fish in quickly. It is also important to
remember that larger fish produce more lactic acid and often
have lower survival after release than smaller fish.

Wounds
are most often caused by hooks. Highest mortalities come from
gill and stomach hookings, followed by intermediate rates
in the lower jaw and eye areas. Lowest mortality occurs with
hooking in the upper lip or jaw or the corner of the mouth.
One of the most effective methods of directing where
fish are hooked is with the use of circle hooks.
These hooks, which are most effective with natural bait, usually
result in hooking in the corner of the mouth. While removal
of circle hooks is a little tricky, it can quickly be done
with a dehooker or a set of pliers.

Generally
speaking, fish taken with live or natural bait are hooked
deeper than those on artificial bait. If an angler
plans to release his catch, be should avoid letting the fish
run with the bait and swallow it before setting the hook.

Surprisingly,
treble hooks usually cause less damage to fish than single
hooks because fish are usually not hooked as deep. This has
been verified for speckled trout and redfish by biologists
with the Louisiana Department of Wildlife and Fisheries. Finally
barbless hooks produce the least damage, both because the
wound is smaller and less handling is required to unhook the
fish.

Fish are
very capable of rejecting hooks, even those in the stomach
or gullet. Interestingly, while stainless steel hooks won't
rust out as quickly as hooks such as tin/cadmiurn, mortality
is lower with stainless, probably because of less galvanic
action.

Many fish,
especially snappers and groupers caught from waters more than
70 feet deep experience depressurization. As water pressure
decreases during retrieval, expanding gases in the fishes'
air bladders forces their stomachs out of their mouths. When
released, these fish float helplessly on the surface. Eventually,
compensation occurs and the fish is able to dive, if it isn't
attacked by a predator first.

Anglers
are often tempted to puncture what they think is the air bladder
protruding from the mouth. This is the stomach and
it should not be punctured, as doing so will kill the fish.
The air bladder can be punctured and vented through the side
of the fish with a hollow needle, if the angler has developed
the skills needed to locate the bladder. Incorrect puncturing
will kill the fish.

Handling
damage should always be minimized. Cut leaders for deep hooked
fish as close to the mouth as possible. Fish small enough
to be picked up by the leader should be unhooked with a dehooking
device. Use wet hands to handle the fish if the fish has to
be handled and never let the fish come into contact with dry
surfaces. Dry hands and surfaces remove the mucus layers of
the fish, allowing bacteria to invade the skin.

Don’t
use a gaff on fish to be released, and if a landing net must
be used, neoprene or knotless twines are best. Minimize the
time out of the water. If the fish are to be tagged have all
tagging materials at hand.

Return
fish to the water gently and if possible, headfirst. If the
fish fails to revive and swim away, the angler should recover
it. Then, with one hand under the bottom of the fish behind
the gill area and the other holding the fish ahead of its
tail, the fish should be deliberately moved backward and forward
to force water over its gills. This should be repeated until
the fish shows signs of recovery. Large fish, such as tunas
or sharks, can be gently towed beside the boat for tagging.
This will force water flow over their gills, helping to revive
the fish.